Pulper with a shaft and method for processing composite materials

ABSTRACT

A pulper with a shaft on which a spiral is arranged has been improved to such an extent that it comprises a shaft with a counter-rotating spiral. Preferably both spirals are arranged on the same shaft. This results in extreme friction in the centre of the reaction space of the pulper and thus in an increase in the capacity of the pulper and in an improvement to achieve highly efficient suspension.

The invention relates to a pulper with a shaft on which a spiral is arranged, and to a method for processing composite materials.

Pulpers with a shaft on which a spiral is arranged are known in a host of different embodiments. In these designs the spiral is used to circulate the materials to be processed in the pulper, in particular of biological materials or paper residues. In the pulper these materials are destroyed by intensive grinding and mixing, and are preferably comminuted to fibres.

Various embodiments of spirals and pulpers are used to achieve optimal mixing and good friction.

It is the object of the invention to improve such a pulper.

According to a first aspect of the invention, this object is met by a generic pulper comprising a shaft with a counter-rotating spiral, wherein the spirals are encompassed by a screen basket.

Such a double pulper comprising two counter-rotating spirals results in highly efficient suspension and preferably complete deflaking. This allows sorting, freeing of accompanying substances and, above all with the use of grinding materials, fibrillating grinding.

With the use of this second, counter-rotating spiral, preferably in conjunction with a feed screw in the upper reaction space, the capacity of the pulper is doubled to trebled. This is due to the fact that the counter-rotating action of the spirals prevents undesirable tangential flow of the material, and consequently increased friction occurs.

A slotted basket in the central region of the pulper promotes the flows of materials. In this arrangement it is possible to use standard baskets from the field of pressure screening systems that are presently commonly available in the market.

An advantageous embodiment variant provides for the two spirals to be arranged on the same shaft. Depending on the design of the spirals, on the rotation of the spiral components and on the direction of the drive of the spirals, different flows arise in the reaction space of the pulper. In this arrangement embodiments are preferred in which in the central region of the reaction space two flows converge, which flows result in the material in this region being subjected to high friction.

It is advantageous if radially of this region an outlet is provided that can be designed as a screen basket.

Such a pulper can in the conventional manner in the lower region comprise a screen plate. However, in the pulper according to the invention the spirals are encompassed by a screen basket.

In particular with the use of a feed opening of a reduced diameter it is proposed that the pulper comprise a feed screw in the upper region of the pulper.

The materials flows are optimised in that the pulper radially outside the region between the spiral and the counter-rotating spiral comprises a slotted basket.

Preferably a known basket of a pressure screening system can be used as a basket.

Such a basket is preferably arranged with different apertures around the spirals.

It is advantageous if the pulper comprises a cylindrical basket.

Similar process control results as is the case in a tube-type reactor are achieved if the pulper comprises several units arranged one behind the other, with each unit comprising at least one spiral and a screen basket.

In this arrangement it is advantageous if the units are interconnected by means of a passage with a feed screw.

In order to be able to feed dilution water between the units it is proposed that in the region of the passage an intake be arranged.

The use of several units makes it possible to design a pulper in such a manner that units arranged one behind the other comprise different baskets.

In this arrangement, units arranged one behind the other can comprise baskets with cylindrical hole regions, wherein the axial length of the baskets varies. As an alternative or cumulatively, it is also possible for the radius of the baskets to vary.

Fibrillating grinding is achieved in that the pulper comprises a basket with grinding media.

Balls and irregularly-shaped grinding media are proposed as grinding media. Depending on the application, different materials are used as grinding media. For example, for processing composite materials, surprisingly, it has been shown that sand as a grinding medium leads to particularly good results. It is therefore proposed that the pulper comprise a basket with sand as a grinding medium. The sand can be a conventional sand that is cleaned as a result of repeated use in the pulper. However, it is also possible to use a quartz sand of a particular granulation that is attuned to the material to be processed.

The characteristics relating to the basket and to the grinding media are significant in the context of the invention, even irrespective of the design of the spirals.

Furthermore, it is the object of the invention to present a method for processing composite materials, in which method the composite materials can in a simple manner be disaggregated into utilisable residues.

This object is met by a method for processing composite materials, in which method the composite materials are placed in a pulper with grinding media, and in that location rejects are separated from fibrous materials. The pulper used for this can, for example, be a pulper as described above.

It has been shown that composite materials such as Tetra Pak packaging can be processed in a conventional pulper in order to separate the fibrous material. This method is facilitated in that grinding media are placed in the pulper. Balls of different sizes and of different geometries and surfaces are suitable as grinding media. A method in which sand is used as a grinding medium has been shown to be particularly advantageous.

In the implementation of the method it is also possible to use a conventional pulper without a screen plate in order to intensively process the composite materials with the addition of sand as a grinding medium. The fibrous materials can be separated in the pulper or subsequently.

After the fibrous materials have been separated, the rejects are separated into a plastic-containing fraction and a metal-containing fraction. In this arrangement the sand can be separated with the metal-containing fraction. Air separators or melting methods can be used as separation mechanisms in order to separate the fractions.

For example in the case of a Tetra Pak composite package, first the fibrous materials can be removed in the pulper. Thereafter the rejects are separated into a plastic-containing fraction containing in particular polyolefins and/or polyethylene, and into a metal-containing fraction containing in particular aluminium. The sand can be separated from the aluminium by means of air separation or by means of a melting process or by means of sieving processes.

This method makes it possible to reuse the materials; a feature which is not possible in the case of incineration or pyrolysis of composite materials.

Several preferred exemplary embodiments are shown in the drawing and are explained in more detail below. The following are shown:

FIG. 1 a cross section of a pulper;

FIG. 2 a cross section of a pulper with a counter-rotating spiral arranged on a further shaft;

FIG. 3 a pulper with several units arranged one behind the other;

FIG. 4 a pulper with several units and water intakes provided between the units; and

FIG. 5 a heavy-rejects trap with radial materials feed and central materials discharge.

The pulper 1 shown in FIG. 1 in its upper region comprises a heavy-rejects trap 2 in order to, with the use of a beater 3, convey heavy rejects radially towards the outside and into the heavy-rejects exit 4, while the more lightweight components find their way in the radially inward region towards the feed spiral 5.

The feed spiral conveys the material to be ground into the reaction space 6 in which a first spiral 7 conveys the material to be ground in the centre of the reaction space upwards so that at the edge of the reaction space it is pushed downwards. Thereafter, further downward, the reaction material enters the zone impinged upon by the counter-rotating second spiral 8, which conveys the material to be ground in the centre of the reaction space downwards, and thus in the radially outer lower region of the reaction space upwards. Thus in the centre region of the reaction space 6 increased friction between the material to be ground occurs.

The material to be ground, in the outer region of the reaction space 6 is then conveyed to the region of the screen-plate basket 11. This screen-plate basket 11 comprises different slot sizes in order to sort the ground material. The ground material is thus conveyed, through different regions 10 of the screen basket with different slot sizes or hole sizes, to different chambers 12, through which it leaves the pulper 1.

In the central region of the reaction space 6 the ground material 9 is conveyed through the central region 10 of the basket 11 to the chamber 12, by way of which it is removed from the system. In the lower region ground material 13 is conveyed to the chamber 14, and in the upper region ground material 15 is conveyed to the chamber 16.

Correspondingly, a multitude of chambers are arranged around the reaction space 6, which chambers make it possible, by way of different slot apertures or hole apertures in the screen basket 11, to remove different grades from the reaction space 6.

A drive (not shown) underneath the pulper makes it possible to rotate the shaft 17, which leads to the reaction space by way of the seal gaskets 18. In this way the counter-rotating spirals 7, 8 convey the material to be ground into the central region of the pulper.

The spirals are designed as counter-rotating spirals and are preferably arranged on the same shaft. In this arrangement the spirals can be designed so that in the region of the shaft they convey the materials towards each other or in the opposite direction. Both approaches result in the materials converging in the central region of the reaction space 6, and consequently being ground by the resulting friction.

The pulper 20 shown in FIG. 2 comprises a first spiral 21 on a shaft 22, and a second spiral 23 on a shaft 24. The shafts 22, 24 are separate from each other so that they can be driven in different directions.

The material 25 to be ground enters the reaction space 26 of the pulper 20 in a manner centrally conveyed by means of the spiral 21. In this reaction space a flow arises which causes friction between the flowing materials to be ground. After such processing the ground material is conveyed as a fibrous material through a cylindrical screen plate 27 into an exit 28 while the residue leaves the pulper by way of an exit 29.

Several of the pulpers shown in FIG. 2 can be arranged in sequence with reaction spaces separated from each other. This results in a tube-type pulper 30 as diagrammatically shown in FIG. 3.

In such a tube-type pulper 30 over the extension of the pipe, in other words over the extension of the individual units 31 to 35, different compositions of the material are measured up to the exit 36 of the tube-type pulper 30.

A good separation process is achieved in that material to be ground moves several times through a single-stage reactor. This is supported by batch operation with external circulation. As an alternative to this, a multi-stage setup is proposed for which, for example, a reactor 30 as shown in FIG. 3 can be used.

The five-stage double pulper with a shaft 37, which double pulper is shown in FIG. 3, makes it possible to achieve a compact design and continuous processing of the material to be ground.

The most stringent demands from the material to be ground can be met with the use of a tube-type pulper 30 with several units in batch operation.

The pulper shown in FIG. 3 can be mounted perpendicularly like the other pulpers shown. To this effect the exit 36 should be closable in order to prevent material discharging from the pulper. As an alternative or cumulatively to this, the exit can also be a pipe reaching to the uppermost level of the pulper so that the aperture of the exit is approximately at the level of the pulper inlet. This prevents a situation in which at the outlet excessive suction arises that would draw the liquid from the pulper.

An advantageous embodiment provides for the pulper to be mounted horizontally so that the units 31 to 35 are situated one beside the other rather than one on top of the other. In this case the pulper can be designed with a relatively short spatial height.

The pulper 40 shown in FIG. 4 comprises three units 41, 42, 43 that are connected in series and are arranged on a shaft 44. The material to be ground is conveyed to the pulper at the inlet 45 and from there into the first unit 41. During processing of the material to be ground in the unit 41 fibrous material 46 is conveyed through a cylindrical screen basket 47. From the first unit 41 the material to be processed is conveyed to the second unit 42 by way of a passage 48. There the material is further processed, and fibrous material is discharged by way of a cylindrical screen basket 49. Finally, the residue is conveyed by way of a passage 50 to a third unit 43 with a further screen basket 51. In this arrangement the axial extension of the screen baskets 47, 49, 51 connected in series continuously decreases.

The pulper 40 comprises three water intakes 52, 53, 54, of which the first water intake 52 is arranged opposite the material 45 to be processed, while the further water intakes 53, 54 are arranged between the units 41, 42 or 42, 43. In this manner the overall materials density in each pulper can be maximised in that as little water as possible is fed in. Nevertheless, more water can be fed in than would be possible if only at the inlet a water inflow 52 were provided.

By means of process control it can be ensured that the friction forces increase from unit to unit. This can be achieved by increased circulation. Consequently it is possible to effortlessly suspend even materials with extremely high specific defibration resistances. The larger free screen areas in the first two units 41, 42 make it possible to easily discharge even fibres from easily defibrable waste papers and already existing free fibres.

FIG. 5 shows a top view and a lateral view of a heavy-rejects trap 60. Such a heavy-rejects trap can be arranged upstream of a pulper in order to mix, isolate, detach, and to separate heavy rejects, if applicable even without pulping effect. If required, the material is shredded and at the entry 61 is conveyed to the heavy-rejects trap 60. At that location the material is impinged upon by a water jet that acts as a propulsion jet 62 so that the particles of the material are isolated. In this process the water of the water jet as dilution water is thoroughly mixed with the particles. By means of ballistic effects, rotating discs 63 and 64 throw the heavier particles along the arrows 65 against a wall 66 of the heavy-rejects trap 60. There they reach a zone 67 with no flow or little flow, in which zone 67 they sink. The heavier particles thus reach the lower exit 68, while the more lightweight particles reach the central exit 69. In contrast to a hydrocylone, in this design the desired effect of separation is less due to centrifugal forces as a result of flow, but rather due to tangential throwing. For this reason smaller device diameters are sufficient.

In such a pulper the processing step of de-inking, in other words the removal of printer's ink, is supported to a large extent. In this process in the first pass the printer's ink is solved from the paper (if applicable with the usual application of chemicals) and is washed out with little water. Little water is used in order to keep the fibre losses to a minimum. In this manner higher degrees of whiteness are achieved than with the known process. This is the case because the remaining size distribution of black particles is moved upwards, and consequently reduced grey shading occurs, because of the reduced specific surface. Ultimately this results in a significantly reduced dwell time in the shear zone (kappa effect).

The conditioner can combine the following process steps in a single device:

1.) Digestion (separation of the compounds) in other words a pulper function.

2.) Deflaking (defibration of all shredded particles or specks).

3.) Sorting (enrichment of the accompanying substances/plastics in the oversized particles; enrichment of free fibre particles in the undersized particles, namely almost 100%). Thus, this corresponds to the function of a so-called final stage screen of conventional materials processing following, or on completion of, a multi-stage sorting cascade.

4.) Grinding, if grinding media (plastic balls) are present. This is a particular advantage in waste paper processing, because balls are able to keep the slots free to an adequate extent. With an adequate free slot area the use of balls is helpful but not mandatory.

5.) Possibly even dispersion, in conjunction with high temperatures. The high temperatures (almost 100° C. at normal pressure; correspondingly higher at higher pressure) would impede grinding (exothermic reaction); however, comminution of the dirt specks (objective of dispersion) would be assisted. 

1. A pulper with a shaft on which a spiral is arranged, wherein it comprises a further shaft with a counter-rotating spiral, or the spiral and a counter-rotating spiral are arranged on the same shaft, wherein in each case the spirals are encompassed by a screen basket.
 2. The pulper according to claim 1, wherein it comprises a feed screw in the upper region of the pulper.
 3. The pulper according to claim 1, wherein radially outside the region between the spiral and the counter-rotating spiral it comprises a slotted basket.
 4. The pulper according to claim 1, wherein it comprises a basket of a pressure screening system.
 5. The pulper according to claim 1, wherein it comprises a basket that is arranged with different apertures around the spirals.
 6. The pulper according to claim 1, wherein it comprises a cylindrical basket.
 7. The pulper according to claim 1, wherein it comprises several units arranged one behind the other, with each unit comprising at least one spiral and a screen basket.
 8. The pulper according to claim 7, wherein the units are interconnected by means of a passage with a feed screw.
 9. The pulper according to claim 8, wherein in the region of the passage an intake is arranged.
 10. The pulper according to claim 1, wherein units arranged one behind the other comprise different baskets.
 11. The pulper according to claim 1, wherein the units arranged one behind the other comprise baskets with cylindrical hole regions, wherein the axial length of the baskets varies.
 12. The pulper according to claim 1, wherein the units arranged one behind the other comprise baskets with cylindrical hole regions, wherein the radius of the baskets varies.
 13. The pulper according to claim 1, wherein it comprises a basket with grinding media.
 14. The pulper according to claim 1, wherein it comprises a basket with sand as a grinding medium.
 15. The use of a pulper according claim 1 for processing composite materials, in which use the composite materials are placed in the pulper with grinding media, and wherein location rejects are separated from fibrous materials.
 16. The use according to claim 15, wherein sand is used as a grinding medium.
 17. The use according to claim 15, wherein after the fibrous materials have been separated the rejects are separated into a plastic-containing fraction and a metal-containing fraction.
 18. The use according to claim 15, wherein after the fibrous materials and the plastic-containing fraction have been separated the grinding medium is separated from the metal-containing fraction. 